And also the public key so that pulling from the new endpoint will work.
This allows other people to host their own attic instances and configure
their (CI) environment to override the default endpoint so e.g. they can
take advantage of a binary cache without having write access to the
official one.
I didn't actually test this change but I think it should work.
Also why'd I format the script like that, ew lol
This will also include attic, so we don't need to explicitly do this
in `./bin/nix-build-and-cache` anymore, which is good because that
script gets called a good number of times and doing that repeatedly was
a bit of a waste.
This will allow most Nix users to use the `default` package and without
having to build from source. And also allows any weirdos to get the OCI
image from the Nix binary cache if they want. No idea why that would be
desireable though lol
